A variety of devices are now commercially available for implantation through minimally invasive techniques. These devices include stents and stent-grafts used to maintain patent flow in blood vessels, the endo-biliary system or the urinary system. These stents and stent grafts have several different forms. Some are in the form of coiled wires while others are made from slotted tubes. Stents are also generally self-expanding or balloon expandable. Typically, they are made from metal and have a few important characteristics. These characteristics include expanded hoop strength, expansion force, expanded and unexpanded diameter, and the amount of foreshortening during expansion. Obviously the art of stent design is to work with these conflicting characteristics in such a way as to form the ideal stent. That stent would require very little force to expand, start with a very small unexpanded diameter and reliably expand to whatever diameter desired and the stent would not foreshorten when expanded.
Another important characteristic of a stent or stent-graft is the amount of expanded stent material that comes into contact with the vessel. Having the surface of the stent in contact with the stent is important because of in-stent restenosis. In-stent restenosis is a phenomenon where, for some reason, the vessel grows through the struts or between the coils and thereby obstructs fluid flow in the vessel. Where the stent is in direct contact with the vessel, the vessel can not impinge on the fluid flow. There is, therefore, a need for a stent which maximizes all of the characteristics above and has as close to 100% vessel contact in the area that is stented as possible.
Another type of device may generally be characterized as aneurysm repair devices. Depending upon where in the body the aneurysm is located, a ruptured aneurysm may be fatal. Typically aneurysm repair devices are used to prevent the aneurysm from getting larger and ultimately bursting. Exemplary types of aneurysm repair devices include those which protect the aneurysm from getting larger by shielding the aneurysm from fluid pressure, covering the neck of an aneurysm, or filling the aneurysm with some sort of packing material. Similar to stents, aneurysm repair devices have a variety of conflicting material characteristics which make them perform better, most notably surface contact or sealing capability. In addition, present coil-shaped repair devices have a potential for the leading edge of the coil to corkscrew into the vessel wall. There is therefore a need for an aneurysm repair device that has good sealing characteristics and one which would be less likely to corkscrew into the vessel wall.
U.S. Pat. No. 5,334,210 describes a prior art vascular occlusion assembly and is depicted in FIG. 1 of the current application. The assembly comprises a foldable material occlusion bag which is filled with a flexible filler. Because the material is not non-compliant, it must be folded and must therefore disadvantageously increase the profile of the device. This bag may be positioned in a blood vessel and is intended to stop fluid from flowing through the vessel. There is therefore no lumen in the device.
Overall there is need for a prosthesis which has nearly complete vessel wall contact while maintaining a patent fluid channel. This prosthesis and its accompanying delivery system would be highly advantageous.